Synthesis of (Ge9–Ge9)6– Dimeric Zintl Ions in Liquid Ammonia Solutions of K4Ge9: Low-Dimensional Coordination Networks in the Crystal Structure of the Ammoniates Kn[K([2.2.2]crypt)]6–n[Ge9–Ge9](NH3)m (n = 2, 3, and 4)


  • In Memory of Professor Hans Georg von Schnering


Three new compounds of the dimeric cluster anion [Ge9–Ge9]6– were obtained from liquid ammonia solutions of the Zintl phase K4Ge9. All of them follow the general formula Kn[K([2.2.2]crypt)]6–n[Ge9–Ge9](NH3)m (1: n = 4, m = 14; 2: n = 3, m = 18; 3: n = 2, m = 17.28) and comprise sequestered and non-sequestered K+ cations in different ratios. The non-sequestered cations coordinate to the Ge9 cages and support the covalent intercluster bond. Additionally, they are in contact with each other by varying numbers of coordinative ammonia bridges leading to arrangement of the anions. The dimensionality of the cluster arrangements correlates with the amount of sequestering molecules. Layers, double chains and single chains are observed for 1, 2, and 3, respectively, according to an increase of [2.2.2]crypt) per formula unit for 1 to 3.